The invention is in the field of tape feeders, particularly feeders for stepwise indexing of tapes having pockets containing surface mountable electrical components.
The tape is advanced stepwise to sequentially present each pocket to a pick-up station where the component is removed from the pocket for subsequent handling such as transfer to a conveyor or direct placement onto a circuit board. Typically, a top cover of the tape is peeled or split to provide access to the component and auxiliary covers or movable "shutters" are provided to prevent loss of components from open pockets.
Several type of supply tapes are presently used. One type has a plastic substrate embossed to define component holding the pockets which are enclosed by a separable thin plastic top cover; and the other type has holes all the way through a cardboard substrate with top and bottom covers for the holes so as to define the component pockets.
Heretofore various attempts have been made to prevent loss of the component from the pocket after removal of the top cover, and the above cross referenced U.S. application Ser. No. 861,977 illustrates an auxiliary cover or shutter for covering the component in the pocket after the top cover of the substrate has been peeled back. The shutter is movable away from the pocket by the feeder mechanism through movement of a shutter supporting link when the feeder is actuated and, thereafter, a vacuum nozzle is advanced into engagement with the top surface of the component for removal from the pocket.
Some component packaging specifications allow for a slight protrusion of the top surface of the component above a top plane of the pocket. Although a shutter may cover the component simultaneously with removal of the top cover of the substrate from the pocket, the case sometimes arises that the bottom surface of the shutter is in engagement with the component in the pocket. Thus, uncovering of the pocket by lateral sliding of the shutter can result in a "tiddlywink" effect wherein the component pops up and is not properly engaged by the vacuum nozzle of the pick and place head. Additionally, flexibility of the auxiliary or integral bottom of the pocket allows it to deform, during packaging of a component having a height greater than the depth of the substrate pocket, so that energy stored in the deformed bottom and the pocket can propel the component out of the pocket when the shutter is opened. Static electricity and vibration are effects which also can contribute to the criticality of the component being engaged by the vacuum nozzle as quickly as possible upon uncovering of the opened pocket.
The above cross-referenced Japanese Patent Disclosures are illustrative of shutters interlinked for actuation with indexing of a tape feeder. Sliding movement is imparted to these shutters to cover and uncover a pick-up station and provide access for pick-up a component from an open pocket.
U.S. Pat. Nos. 4,494,902 and 4,620,655, cross-referenced above, teach relative sliding movement between a plate and a pick-up station in order to allow removal of a component through an opening in the plate in timed relationship with actuation of the feeder. U.S. Pat. No. 4,606,117 discloses engaging and opening of a shutter by a protruding portion of a pick and place head during lateral movement of the head between pick-up and placement stations, as illustrated in FIGS. 18 and 20 thereof.
None of the cross-referenced prior art suggest or teach opening of a shutter by the pick and place head while it is advancing the vacuum nozzle into engagement with a top surface of the component so as to minimize the period of time during which the component is uncovered before engagement by the vacuum nozzle. In contradistinction, the instant invention is particularly directed to such a method of actuating the shutter and the apparatus for accomplishing such method.
Accordingly, it is an objective of this invention to provide a method and apparatus for preventing loss of components from opened pockets prior to their removal by the vacuum tube of a pick and place head or the like.
Details of the manner of accomplishing the objectives of the invention will become apparent from the disclosure that follows.